Submarine signaling device



SUBMARINE SIGNALING DEVICE Filed Feb. '10, 1944 6 Shee ts-Sheet 1 .99 L.G. BOSTW/CK 1 INVENTORS J H K ATTORNEY Dec. 3, 1946. e. BOSTWICK ET AL2,411,355

SUBMARINE SIGNALING DEVICE Filed Feb. 10, 1944 6 Sheets-Sheet 2 LGBOSWCK'"Z J; H; KING ATTORNEY Dec. 3, 1946. 1.. G. BOSTWICK ETAL 2,411,365

SUBMARINE SIGNALING DEVICE Filed Feb. 10, 1944 6 Sheets-Sheet 3 Dec.3,1946.

L. e. BQSTWICK ETAL 2,411,865 SUBMARINE SIGNALING DEVICE I Filed Feb.10, 1944 6 Sheets-Sheet 4 L. a. BOSTW/CK ATTORNEY i... G. BOSTWICK ETAL.

SUBMARINE SIGNALING DEVICE Filed Feb. 10, 1944 6 Sheets-Sheet 6 FIG. 8

1.. G. BOSTW/CK J. H KING A T TOR/V5 r" wvEivToRs Patented 3,-

Lee G. Bostwick and Jo E. s-1 gnors to Bell Telephone Laboratorlw,

g, Cbatham, 1

Incorporated, New York, N. Y a coratlon or New York This inventionrelates to submarine si naling it, ran, SerialNc. 521,782

devices and more particularly to high power pro-- jectors of the directradiating diaphragm type especially suitable for the propagation of lowfrequency signals.

The attainment of high i tensity signals in a submarine signaling deviceor the diaphragm type entails, inter alia, the use of a diaphragmsubstantial area and capable oi large amplitude vibrations. In addition,in devices operable at low frequencies, the diaphragm must have a supprevent net displacement of the diaphragm of aphragm due to variationsin the hydrostatic pres sure thereon but is not actuated in response tovibrations of the diaphragm at frequencies within the operating range ofthe signaling device.

In accordance with a further and specific feature of this invention,thelinkage between the.

diaphragm and the microswitch includes a me-' chanical filter element ofsuch. parameters that the microswitch will be actuated only in responseto displacements of the diaphragm at frequencies below the lowestfrequency in the range the signaling device is intended to translate.

submarine signaling device due to hydrostatic.

pressures while allowing large amplitude vibrations of the diaphragm inaccordance with signal forces applied thereto.. More specifically, oneobject of this invention is to compensate accurately and quicklyforvariations in hydrostatic pressures acting upon the diaphragm of asubmarine signaling device, to maintain the diaphargm in its normalneutral position In accordance with one feature of this invention, asubmarine signaling .device comprising a diaphragm having one surface incommunication with the sea and the opposite surface enclosed by ahousing, is provided with a chamber or reservoir containing a gas underpressure and with means actuated by the diaphragm for releasing gas fromthe chamber into the housing or from the housing into the seato maintainequality between the pressures acting upon the opposite surfaces of thediaphragm.

In accordance with anothervfeature of this invention, the aforesaidmeans includes a solenoid operated valve coupling the chamber to theinterior. of the housing and a microswitch for controlling theenergizing circuit for the solenoid of the valve, and a mechanicallinkage between the diaphragm and the actuating element of themicroswitch is provided, the linkage being constructed and arranged sothat the switch is operated in response to displacements of the dia- Inone and particularly advantageous construction, the filter elementcomprises a spring integral with the diaphragm and coupled to amechanical resistance defined by a. paddle member cscilv latable in abody of highly viscous liquid.

The invention and the above-noted and other I features thereof will beunderstood more clearly and fully from the following detaileddescription with reference to the accompanying drawings in which:

Fig. l is a perspective view of a submarine sis= this invention;

naling device illustrative of one embodiment of' Fig. 2 is a side viewmainly in section of the signaling device shown in Fig. 1;

Fig. 3 is a rear view of the device shown in Figs. 1 and 2, aportion' ofthe back of the housing and a part of the reservoir being removedi Fig.'4 is a detail view in section along plane 5-5 of Fig. 3; Y

Fig. 5 is a detail perspective view of the solenoid operated valve andthe actuating system for the switch therefor. a portion of themechanical impedance element included in this system being broken awayto show details of construction:

Fig. 6 is a top view of the impedance element;

Fig. 7 is a side view mainly in section of a submarine signaling deviceillustrative oi another embodiment of this invention;

Fig; 3 is a rear view of the device shown in Fig? with a portion of thehousing removed;

and

Fig. 9 is a perspective view of the control systeam for the valves inthe device illustrated in I Figs. '3 and 8. I

Referring now to the drawings, the submarine signaling deviceillustrated in Figs. 1 to 6 in elusive comprises a ru ged housing 20,for example cast of-metal, provided with mounting lugs ti and havingsecured in fluid-tight relation'to the front end thereof, as by aplurality. of bolts 22, an annular face plate 23 which mounts a signaltraiatpa unit. This unit, which advantageously is of 'the' moving coiltype as shown in Fig. 2, comprises a magnet assembly including coaxialpole-pieces 24 and 25 defining an annular gap .26. The pole-pieces areclamped against opposite ends of a cylindrical permanent magnet 21 byscrews 28 and are maintained in accurate coaxial relation by anon-magnetic spacer ring 29.

Secured to the poleepiece 25, as by houses,

is a shallow, apertured, dished, non-magnetic frame 3| which is securedalso vtothe face plate 23 as by bolts 32. An annular diaphragm, forexample of metal such as beryllium copper, includes an intermediateconcavo-convex portion 33 and irmer and outer portions 34 and 35, re-

spectively, of sufficient flexibility to allow free vibration of theintermediate portion 33 as a whole analogous to a piston. The peripheralpart of the outer portion 35 is clamped to the frame 3| 'by a ring 36and the inner edge part of the inner flexible portion 34 is clampedagainst a pnotuberance 31 on the pole-piece 24 by a nonmagnetic ring 38.Thediaphragm has aflixed thereto a cylindrical mount 39, for example ofinsulating material, such as phenol'fabric, which extends into the gap26 and carries a. driving coil 40.

Over-lying the diaphragm and secured in intimate engagement with theintermediate portion 33 thereof is a protective membrane or diaphragm4|, for example of gum rubber, the peripheral part of which isclampedbetween the face plate 23 and the ring 36 and the central portion ofwhich is clamped against the ring 38 by a non-magnetic stud 42 flxed inposition by a bolt 43. The diaphragm 4| serves as a sound barrier atfrequen cies up to several hundred cycles per second and has a flutedportion |||l therein to increase its flexibility.

Electrical connection to the coil 40 and we microswitch describedhereinafter may be established by way of a cable, a portion of which is--shown at 44 in Fig. 2, which enters the housing 20 through a suitablewater-tight stufling box 45.

When the submarine signaling device is submerged, the diaphragm 33 issubjected to hydrostatic pressures which might deleteriously affect theoperating characteristics of the device and which might be of suchmagnitude, particularly when the device is utilized at great depths, asto distort or even destroy the diaphragm. In accordance with a featureof this invention, means are provided for counteracting the hydrostaticpressure upon the diaphragm to maintain the steady pressures effectiveupon the two faces of the diaphragm in equilibrium.

As shown in Fig. 2, the housing is provided with a substantiallyhemispherical wall 46, which may be cast integrally with the housing,and a cover member having a substantially hemispherical Wall 41concentric with the wall 46 is secured in fluidtight relation to therear of the housing, as by bolts 48. The two walls 46 and 41 bound afluidtight chamber or reservoir 49 into which gas,

such as air, under substantial pressure may be introduced through avalve 50 and from which gas may escape into the housing 20 by way of aport 5| in the wall 46. Threaded into the port 5| is a coupler member 52through which communication is established from the chamber 49 to oneside of a solenoid operated valve 53 of conventional construction, thevalve having a restricted outlet coupling 54, shown in Fig. 3, incommunication with the interior of the housing 20. The valve, togetherwith the sol noid 0- tuating element 55 therefor is supported by a rigidbracket 58 secured to connection to the solenoid is established by wayof a cable 51. The construction is such that normally, that is, when thesolenoid is deenergized, the valve is closed, and when the solenoid isenergized, the valve is opened and gas from the chamber 49 flows intothe housing 20. a

The solenoid energizing circuit includes a microswitch 58, shown inFigs. 4 and 6, which is mounted on a supporting strip 59 and is actuatedby a linkage extending from the diaphragm, illustrated in Figs. '4, 5and 6. As shown most clearly in Fig. 5, the outer 'flexible portion 35of the diaphragm includes a finger or spring member 60 to which a drivepin 8| is aflixed, the

pin extending through but not touching an aperture reducing bushing 90afllxed to the frame 3|, and into engagement with the actuatingelementof the microswitch 88. Associated with the filled with a highlyviscous fluid, for example an on known commercially as Vistac, and hasaffixed thereto by a cap a resilient sealing member 66, for example ofneoprene. Immersed in the fluid filling is a cylindrical paddle member61 which is supported by a rocker element 68 having an arm 69 providedwith an aperture i0 through which the drive pin 6| extends. The arm 69has threaded thereinto a pair of aligned cone pivots 1| engaging thedrive pin 6|. The rocker element 68 has threaded thereinto a pair ofcone pivots 12, which are aligned 'and'positioned substantially in theplane of the sealing member 66 so that the stiffness reaction of themember 66 is minimized andhigh sensitivity compensation is obtained.Motion of the paddle member 61 through the viscous fluid develops a highmechanical resistance, as is apparent.

The casing 62 is provided with an arm." to which the mounting strip 58for the microswitch 58 is secured by screws 14.

The mechanical resistance element and the spring arm 60 are constructedand arranged so that the rod 6| moves in response to even small changesin the hydrostatic pressure effective upon the diaphragm but remainssubstantially stationary when the diaphragm vibrates in response.

to signal currents supplied to the driving coil therefor. The principlesinvolved will be understood from the following considerations.

The rod 6| is moved in response to displace-' constitutes a resistancein parallel with the stifi- I ness noted. The stiffness and resistancedefine a mechanical filter so that, as will beapparent, the motion ofthe rod 6| as afunctionof frequency will be dependent upon the constantsof the filter.

These constants may be correlated to effect discriminatlon against adesired range of freq'u'en cies. Specifically, in a device of theconstruction described, the parameters involved are correlated so thatthe filter discriminates against frequencies-in the intended operatingrange of the device, whereby the rod 6| is moved in response to steadydisplacement of the diaphragm or vibration thereof below the operatingrange,

the housing 2|). Electrical aera'ece but motion of the rod is preventedin this range. In a particular device of the construction .describedhereinabove and intended to operate most 'emcientiy in the range from 20to 350 cycles per second,'a filter wherein the stiffnesswas of apment inthe operating rangewas several times that below this range.

When the submarine signaling device is submerged, the diaphragm isdisplaced inwardly due to the increasing'hydrostatic pressure thereon.This displacement of thediaphragm results in motion of the drivingpin6;] as described above,

so that the microswitch contacts are closed and the solenoid 55 isactuated to open the'valve 53,

whereby air under pressure flows from the chamber 49 into the housing20. Thus, the pressure I acting upon the rear face of the diaphragm 'isincreased. when the latter pressure is equalto the hydrostatic pressureupon the front face of the diaphragm, the diaphragm is returned to, its

initial position, the microswitch operates to open the solenoid circuitand the valve 53 closes.

' Hence, the diaphragm is maintained in-its normal neutral position foroperation at any desired depth. In a specific construction, it has beenfound that the me a position of the diaphragm is maintained within10.010 inch, while vibra-'- tional amplitudes of the diaphragm, inaccordance with signals, of at least ten'times this value are permittedwithout operation of the microswitch.

When the signaling device is raised, the pressure within the housing isreduced automatically to maintain equilibrium between the pressures uponopposite sides of the diaphragm; For this purpose, there is provided avent which comprises a coupler 1:8 threaded into the housing 2% andhaving therein a bore 11 and a recess 78, the latter having a port-I9communicating therewith. Secured in water-tight engagement with thecoupler it. is a cap 86 into which a slender tube 8| communicating withthe bore I1 extends. A sec-' ond open-ended slender tube 82 extends fromthe port it and isaffixed upon the housing by brackets or clamps 88.Disposed within the recess and positioned by four pins 88 is a floatableball at over which a disc 88 having a restricted central opening ispositioned.

- Whenthe pressuresupon opposite sides of the realized. Attainment ofhigh power capacity requires the use of a fairly large diaphragm,largevibrational amplitudes and a driving coil capable of dissipating theheat generated therein when signal currents requisite for thevibrational amplitudes involved are supplied thereto. In a specificdevice intended for operation in the range noted above and capable ofproducing root mean square sound pressures of the order of 300ildynesper square centimeterat a distance of 1 foot from the front of thedevice, .a diaphragm wherein the inner and outer diameters of the bodilyvibratile portion 33 are approximately 3 inches and 8 inches,respectively, this portion was vibratile at amplitudes of the order of0.41 centimeter from its neutral position and a driving coil capable ofradiating of the order of 125 watts as heat have been foundsatisfactory.

The response frequency characteristic of the devicewill be determined bythe mechanical constants of the diaphragmand the parameters of theacoustic elements associated. therewith. In a construction foundparticularly satisfac-- tory, the diaphragm constants were such that theresonance frequency of the diaphragm was approximately 23 cycles persecond in open water, the eflective mass of the vibratory system beingapproximately 450 grams and the stiffness of the suspension. portionstdandtfi being approximately 48x10 dynes per centi- 4 The diaphragmresonance may be damped by a plurality of acoustic resistances,twometer.

of which are shown on Fig. 2, each defined by a metallic cylinder 8?provided with a multiplie ity of fine .slets, fitted in the apertures inthe frame ti and closed at one end by a cap 88. The

frame 88 is imperforate except for the openings frequency. Thelargechamber bounded bythe' a housing to and the frame at is made ofsuch volume that varlationsin its stiffness when the signaling deviceis. submerged to a prescribed depthdo not alter the resonance frequencyof the vibratory system by more than of the order of 10 per cent.Inaspeciflc construction, a chamber having a volume of the order of 19X10? cubic centimeters has been found satisfactory, resulting in a changeof not more than 10 per cent in diaphragm are equal, the hydrostaticpressure within the cap 8d established by way of the tube- 82,coun'terbalances the pressure within the cap due to the air within'thehousing 26. If the signaling device is raised, the pressure within thehousing exceeds the hydrostatic pressure so that air is released fromthe housing by way of the port it and tube 82 until equilibrium betweenthe two pressures is established.

The ball 85 in cooperation with the disc 85 constitutes a check valve toprevent flooding of the cap to and flow of water into the housing 2c inthe event of failure of the compensation.

As has been noted hereinabove, in a specific device of the constructiondescribed, the intended operating range is substantially 20 to 350cycles erating range and high power capacity are to be the resonancefrequency of the vibrating system when the device is submerged to adepth of 50 feet. With such device, a sound field wherein the pressureis constant within 511.0 decibel over the operating range from 20 to 350cycles per.

second has been obtained.

The submarine signaling device illustrated in Figs. 7 to 9 is ofgenerally the same construction as that illustrated in Figs. 1 to '6,inclusive, and

described hereinabove but differs therefrom in the control system foreffecting compensation for variations in the hydrostatic pressure uponthe diaphragm. Specifically, the compensating .system included in thedevice illustrated in Figs.

7 to 9 comprises the solenoid controlled valve- 53 for allowingflowofair from the reservoir (it into the interior of the housing 2@ tocounteract hydrostatic pressures acting upon the diaphragm, and a secondsolenoid controlled valve 8i having a restricted inlet land having itsoutlet con.- nected by a pipe 93 to the vent 9d, the valve 9i. whenopen, allowing release of air from the interior of'the housing 20 whenthe air pressure within the housing exceeds the hydrostatic pressuresupon the diaphragm. The vent 94 may bi! similar to the vent 80 andprovided with an outlet 95. The energizing circuit for the solenoid ofvalve 53 includes the microswitch 58 and that for the solenoid of valve9| includes a similar microswitch 96, the two microswitches beingmounted upon a support 91 secured to the polepiece 24.

The support 91 comprises parallel arms 98 from which a rocker member 99is supported by trunnions I90. The rocker member includes a pair oftransverse strip members NH carrying adjustable contactors I 02' forengaging the actuating buttons of the microswitches, and carries at itsends weights I93, the purpose of which will be pointed out hereinafter.and weights are constructed and arranged so that normally the rockerassembly is balanced with respect to the trunnions and the contacts I92are spaced slightly from the actuating buttons of the microswitcheswhereby, normally,

both solenoids 55 are" deenergized and both the valves 53 and 9| areclosed. The rocker 99 is actuated by the drive pin 6| by way of agenerally U-shaped spring I04 which has its opposite ends secured to thedrive pin and the rocker member.

Briefly, the operation of' the compensating system is as follows: Asnoted heretofore, normally, that is, when the diaphragm is at itsneutral position, both valves 53 and 9| are closed.

When the signaling device is submerged, due to the increasinghydrostatic pressure thereon the diaphragm is displaced inwardly so thatthe rocker member 99, driven by the pin BI, is tilted in the clockwisedirection to operate the microswitch 58, thus causing the valve53 toopen. Air from the chamber 49 flows into the interior of the housing 20to counteract the hydrostatic pressure upon the diaphragm, until thediaphragm is returned to its neutral position. If the pressure withinthe housing 29 exceeds the hydrostatic pressure on the diaphragm, asoccurs when the signaling device is raised, the diaphragm movesoutwardly so that the rocker member 99 is tilted in the counterclockwisedi-'- rection to cause operation of the microswitch 96. Consequently,the valve 9| is opened. and air escapes from the housing through thevent 94, 95 until the diaphragm is restored again to its neutralposition. Thus, equilibrium between the static pressures acting upon theopposite sides of the diaphragm is maintained.

The actuating means for the microswitches constitutes a mechanicalsystem which discriminates between slow or very low frequency displacement of the diaphragm and vibration thereof at higher frequencies,whereby the micro: switches are operated only in response todisplacement of the diaphragm at frequencies below the lowest frequencyin the intended operating frequency range of the signaling device.

It will be apparent from-a consideration of the mechanicalsysteminvolved in the operation of the rocker 99 that the motion of the rockerin relation to frequency of displacement of the diaphragm will bedependent upon the parameters of the rocker, spring I and spring arm' 90con-' sidered as mechanical impedances. The rocker is essentially amass, the major portion of which is provided by the weights I93, and thespring I04 and spring arm 60 are essentially stiffnesses. The threeelements noted constitute the essential The rocker member impedances ofa mechanical mesh associated with the diaphragm. If these impedances arecorrelated so that the resonant frequency of the mesh is well below theintended operatin range of the device, the rocker 99 will remainsubstantially stationary when the diaphragm vibrates at frequencieswithin this range but will be tilted, in the manner described above, inresponse to changes in hydrostatic pressure upon the diaphragm, toeffect operation of the microswitches and thus result in equalization ofthe pressures acting uponopposite sides of the diaphragm. In aparticular device intended for operation in a range of frequencies from20 cycles per second up, the impedances may be correlated so that themesh noted is resonant at about 6 cycles per second.

In some cases, dissipating or mechanical resistance elements may beprovided in association with the rocker arm 99 to increase thediscrimination between vibrations of the diaphragm at the intendedoperating frequencies of the device and at lower frequencies, as totheir effect upon the rocker arm.

Although specific embodiments of the invention have been shown anddescribed, it will be understood that they are but illustrative and thatvarious modifications may be made therein without departing from thescope and spirit of this invention as defined in the appended claims.

tions in hydrostatic pressure upon said one face to maintain thepressures on said one and opposite faces substantially equal, saidcompensating means comprisin a, reservoir containing a gas underpressure, a normally closed valve between said reservoir and saidchamber and means actuated in accordance with displacement of saiddiaphragm only at frequencies below a preassigned frequency and in thedirection corresponding to increase in said hydrostatic pressure foropening said valve.

2. A submarine signaling device comprising a diaphragm having one facefor communication with the sea, said diaphragm having a bodily vibratileportion and a. flexible mounting portion, means defining a chamber withthe opposite face of said diaphragm, signal translating means c0-operatively associated with 'said diaphragm, a reservoir containing agas under pressure, a valve for coupling said reservoir to said chamber,actuating means for said valve, and means including a driving elementcoupled to said flexible mounting portion of said diaphragm foroperating said actuating means to open said valve when the pressure uponsaid one face exceeds that upon said opposite face.

3. A signaling device for translating signals within a preassignedoperating frequency range, comprising a diaphragm, means defining achamber with one faceof said diaphragm, a reservoir containing a gasunder pressure, a valve coupling said reservoir to said chamber,actuating means for said valve, and means for operating said valve inresponse to displacement of said diaphragm only at frequencies below theoperating frequency range of the device, said operating means comprisinga driving member coupled to said diato displacement of said diaphragm atfrequencies below the operatingfrequency range of the device, saidoperating means including a mechanical resistance-stiffness filteractuatedby said diaphragm.

5. A signaling device for translating signals within a preassignedoperating frequency range,

comprising a diaphragm, means defining a, cham-- her with one faceofsaid diaphragm, a reservoir containing a'gas under pressure, a valvecoupling said reservoir to said chamber, and means for l actuating saidvalve only in response to displacementof said diaphragm at frequenciesbelow the operating frequency range of-the device, said actuating meanscomprising a mechanical linkage actuated in response to displacement ofsaid dia'phrgam and including a mass and a stiffness resonant at afrequency below said range.

6. A signaling device for translating signals within a preassignedoperating frequency range,

comprising a diaphragm, means defining a chamber with one face of saiddiaphragm, and'means for maintaining substantial equilibrium between thepressures upon said one face and the opposite face of said diaphragm,said equilibrium maintaining means comprising means responsive only todisplacement of said diaphragm at frequencies below the. operating rangeof the device for increasing the pressure in said chamber when thepressure upon said .one face is less than that upon said opposite faceand means for decreasing the pressure in said chamber when the pressureupon said one face exceeds that upon said opposite face.

'7'. .A. signaling devicein accordance with claim 6 wherein saidpressure increasing means comprising a reservoir containing a gas underpressure, a valve coupling said reservoir to said chamber, operatingmeans for said valve, and means for actuating said operating means inresponse to displacement of said diaphragm including a mechanical filterelement coupled to said diaphragm. 8. A signaling device in accordancewith claim 6 wherein said equilibrium maintaining, means comprises areservoir containing a gas under pressure, a valve coupling saidreservoir to said chamber, a venting valve for said chamber, and meansfor operating said first and second valves to open said first .valvewhen the pressure upon said one face is less than that upon said oppo-site'face and to open. said second valve when the pressure upon saidone face is greater than that upon said opposite face, said operatingmeans comprising a mechanical impedance element coupled to and actuatedin response to displacement of said diaphragm and including mass andstifl ness resonant at a frequency below said operating range.

9. A signaling device comprising a diaphragm having a flexibieportion,means defining a chamher with one faceof said diaphragm, a reservoircontaining a gas under pressure, a normally closed solenoid operatedvalve coupling said reservoir to said chamber, control means for thesolenoid including a switch, a driving member coupled to said flexibleportion of said diaphragm and to the actuating element of said switch, acontainer earnest having therein a viscous fluid, 'a paddie memberimmersed in said. fluid, and -means connecting said paddle member tosaid driving member,

10. A submarine signaling device for translating signals within apreassigned operating frequency range, comprising a diaphragm having oneface for communication with the sea, means defing a chamber with theopposite face of said diaphragm, and means for compensatifig for hydro-Y 10 static pressure upon saidone face, said means comprising areservoir containing a as under pressure, a valve coupling saidreservoir to said chamber, means for operating said valve and actuatingmeans for said operating means responsive only to displacement of saiddiaphragm at frequencies below the operating range of the device, saidactuating-means including a casing containing'a viscous fluid, a paddlemember oscillatable in said fiuid and a driving connection to i saidpaddle member including a spring actuated by displacement of saiddiaphragm.

11. A submarine signaling device for translat ing signals within apreassigned operating frequency range, comprising a diaphragm having oneface for communication with the sea, said diaphragm having'aiso a springportion adjacent its periphery, means defining a chamber with theopposite face of said diaphragm, a reservoir containing a gas underpressure, asclenoid opher, a microswitch for controlling energization ofthe solenoid for said valve, and means for actuating said switch toeffect opening of said valve said diaphragm at frequencies below theoperating range'of the device and comprising a mechanical frequencydiscriminating linkage ineluding said spring portion, between saiddiaphragm and theactuating element of said switch. 12. A submarine-signaling device in accordance with claim 11 wherein said linkageincludes in addition to said spring portion a highly viscous body and apaddle member immersed in said body and connected to said springportion,

13. A submarine signaling device in accordance with claim 11 whereinsaid linkage com-- prises in addition to aid spring portions. sunnesselement and a mass element, the combination of said stiffness and masselements and said spring portion being resonant, at a frequency belowsaid operating range.

14. A submarine signaling devic for translating signals withinapreassigned operating frequency range, comprising a diaphragm one faceof which is adapted to be exposed to the sea, signal translating meanscooperatively associated with said diaphragm, means defining with saiddiaphragm a chamber opposite the other face thereof, a second chambercontaining a gas under pressure, valve means connecting said chambers,

relief valve means associated with said first chamber, actuating meansoperable in response to displacement of said diaphragmfor controllingsaid first and relief valve means to maintain the pressure upon saidother face of said diaphragm substantially equal to the pressure on saidone face thereof,'and means for preventing operation of 7 said actuatingmeans in response to vibrations. of

said diaphragm at frequencies within the operating range of the device.15. A. submarine signaling device for translatingsignais within apreassigned operating frequency range, comprising a diaphragm havingerated valve coupling said reservoir to said cham- 11 one face forcommunication with the sea, means defining a chamber with the oppositeface of said diaphragm, a first solenoid operated valve for venting saidchamber, a microswitch for the solenoid of said first valve, a reservoircontaining a gas under pressure, a second solenoid operated valvecoupling said reservoir to said chamher, 'a second microswitch for thesolenoid of said second valve a rocker member for operating said firstand second switches, means for tilting said rocker member to actuatesaid first switch when the pressure upon said opposite face exceeds that12 upon said one face and to actuate said second switch when thepressure upon said one face exceeds that upon said opposite face, saidtilting means includin a connection between said diaphragm and saidrocker member and having a stiflness therein, and mass means carried bysaid rocker member and resonant with said stiffness at a a. frequencybelow the operating 'range of the device.

- LEE G. BOSTWICK.

JOHN H. KING.

